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Lactate is a product of energy metabolism and can also serve as a fuel source. It is present in the blood stream during rest and increases as a person incrementally transitions from walking, then jogging, and progressively faster running speeds. There becomes a point when the runner will begin to produce lactate quicker than will diffuse from the blood. This is referred to as the lactate threshold. Once this threshold is reached the concentration of lactate in the blood rises sharply and is associated with fatigue and exhaustion.
Why is the Lactate Threshold Important?
- Lactate threshold has been shown to be superior to maximum oxygen uptake (Vo2 max) when assessing endurance performance (homogeneous groups).
- There is a strong correlation between lactate threshold and endurance running performance.
- If a runner is able to run at a greater speed before reaching lactate threshold they should be able to hold a faster race pace before fatigue.
How can Lactate Threshold be determined?
Lab testing would be the gold standard but several field tests have been proposed. One field test that has been shown to be fairly accurate in ccompetitivedistance runners and triathletes is the 30 minute time trial. Both heart rate and running velocity at the lactate threshold can be accurately obtained. As a general reference if training feels “somewhat hard” then the runner is probably running at the lactate threshold. Training just above lactate threshold would be consider “hard” to “very hard”.
30 Minute Time Trial
Equipment: Treadmill, Heart Rate Monitor, Something to cover distance and possibly time on dash board
Methods
- Cover indicators of kilometers per hour
- Perform a self selected warm-up
- Set the treadmill to a 1% grade
- Gradually increase running speed to a self-selected pace that would be sustained for 30 minutes
- Once at the self selected 30 minute race pace the trial begins
- Running speed can be adjusted at any time
- If somebody is helping administer the test the runner should be told the time every 5 minutes (if administering alone an uncovered timer on the treadmill should be acceptable)
- Heart rate is taken every 5 minutes
- The runner should NOT BE AWARE of the distance covered until the end of the test
Once the test is completed the distance covered in kilometers(km) should be divided by o.5 hours (h). This is the average running velocity (km/h) and can be used as an estimate of the lactate threshold. The average heart rate taken during the final 20 minutes can be used to estimate the heart rate at lactate threshold.
Training to improve lactate threshold
It is common for runners to train with intervals or continuously at or above their lactate threshold to affect improvements in endurance performance. The following is a modification of a long interval training program that has been demonstrated to improve lactate threshold and time to exhaustion in less well trained and some well trained endurance athletes. It is adapted from Demarle et al., 2003.
Sample Program
Calculate running velocity (km/h) at lactate threshold using 30 minute time trial. Once this is determined the intensity of the long intervals can be calculated.
1. Calculate velocity (intensity) of intervals: Both the intense and rest intervals will need to be calculated.
- Intense Interval=Velocity at Lactate Threshold+1km/h (e.g. 16km/h+1km/h=17km/h)
- Rest Interval= 0.55 X velocity lactate interval (e.g 17 km/h X 0.55=9 km/h)
So, if a runner’s velocity at lactate threshold is 16 km/h then simply add 1km/h and this determines how fast to run for the interval. Once the calculation for the intense interval is completed the “rest” interval would be approximately 1/2 of the speed of the intense interval.
2. Intervals Intervals would alternate high and low intensity. Higher intensity intervals would be run at:
- 5 minutes for less well trained runners
- 6 minutes for highly trained runners
Lower intensity/rest intervals would be run at:
- 2.5 minutes for less well trained runner
- 3 minutes for highly trained runners
One Full Interval Would=High Intensity+Rest Interval
3. Weekly Training Less well trained individuals would train as follows 2 times a week for 4 weeks.
_____________Week 1______Week 2______Week 3______Week 4
1st session 4 Intervals 3 Intervals 4 Intervals 5 Intervals
2nd session 3 Intervals 4 Intervals 5 Intervals 8 Intervals
Trained individuals would train as follows 2 times a week for 8 weeks.
_____________Week 1______Week 2______Week 3______Week 4
1st session 4 Intervals 3 Intervals 3 Intervals 3 Intervals
2nd session 2 Intervals 2 Intervals 2 Intervals 6 Intervals
_____________Week 5______Week 6______Week 7______Week 8
1st session 4 Intervals 4 Intervals 4 Intervals 4 Intervals
2nd session 5 Intervals 5 Intervals 5 Intervals 5 Intervals
Program Expectations
Less well trained individuals can expect to improve their velocity at lactate threshold and subsequent time to exhaustion with this program. From the study this was adapted, 1/2 of the well trained individuals demonstrated improvement in velocity at lactate threshold performing this protocol 2 x’s a week. Experienced runners that do not perform higher intensity training will likely benefit more than those who already incorporate higher intensity training.
Bottom Line
- If a runner is able to run at a greater speed before reaching lactate threshold they should be able to hold a faster race pace before fatigue.
- Training can improve lactate threshold.
- Velocity and heart rate at lactate threshold can be accurately assessed with the 30 minute time trial.
- 30 minute time trial can be used to test and re-test if training interventions are improving lactate threshold.
References